1. Field of the Invention
This invention relates to a magnetic tape magazine, and more particularly to a magnetic tape magazine in which a pair of elastic cushion sheets are interposed between the side faces of tape convolutions wound on a pair of cores, and the inner faces of the casing thereof.
2. Description of the Prior Art
In order to minimize the size of magnetic tape recorders, it is necessary to make the size of the magnetic tape magazine used therein as small as possible. In order to reduce the size of the magnetic tape magazine while providing the longest possible play time, it is necessary to manufacture thin long-play magnetic tapes. Long-play magnetic tapes should best be mirror finished to carry thereon a magnetic recording material with high density. The mirror finished thin magnetic tape is apt to jam and is hard to wind up on a core so that the side faces of the coiled tape are perfectly flat. For instance, the side faces of the tape convolution are apt to be curved or rough.
Particularly, when the tape is quickly advanced in the magazine or rewound at high speed, the side faces of the tape rub the inner face of the walls of the casing of the magazine, so that back tension on the tape increases when the tape is advanced in playing or recording.
Because of the increased back tension on the tape, the edges of the tape are permanently deformed and the recorded signal carried on the tape is degraded in quality, and accordingly the quality of reproduction is lowered.
In order to obviate the above mentioned defects, there has been proposed a magnetic tape magazine in which a pair of elastic cushion sheets are interposed between the side faces of the tape convolutions and the inner face of the casing thereof as disclosed in U.S. patent application Ser. No. 723,369, now U.S. Pat. No. 4,101,096. The cushion sheets press the side faces of the tape convolutions with a constant pressure whereby the tape is wound smoothly with small back tension into convolutions having flat side faces.
The cushion sheets can be made of an elastic material such as a formed plastic sheet material or synthetic paper. The material can be used mixed with lubricant or antistatic agent or used with lubricant or antistatic agent applied thereto. The thickness of the cushion sheets can be selected from between about 50 to 150.mu. according to the shape, structure and material thereof.
As is well known in the art, the magnetic tape magazine includes a casing comprising upper and lower halves which are coupled together in superimposed relation to form a space therebetween for receiving the tape convolutions therein. Heretofore, said cushion sheets have been supported on the inner face of the respective halves of the casing by means of holes provided therethrough and vertically extending rod-shaped projections integrally formed on the inner face of the corresponding half of the casing and inserted into said holes.
When the magnetic tape magazine is assembled, the cushion sheets are put on the respective halves of the casing with the holes and the projections engaged with each other before the halves are superimposed.
The magnetic tape magazine of this type has been found to be satisfactory in use. However the assembly of the tape magazine involves a difficulty in that, when superimposing the halves of the casing with one of them directed upwardly and the other directed downwardly, the cushion sheet supported on the upper half is apt to fall therefrom since the cushion sheet is held only by the force of friction between the side face of the vertically extending rod-shaped projections and the walls of the holes. Therefore, it has heretofore been very difficult to use an automatic system to assemble the magnetic tape magazine having cushion sheets.
There also has been proposed a magnetic tape magazine in which additional retaining members are provided on said rod-shaped projections to prevent the cushion sheets from falling from the upper half of the casing. The additional retaining members are secured to the free end of the rod-shaped projections by means of adhesive or welding after the cushion sheets are positioned on the respective halves of the casing.
However, this type of magnetic tape magazine is disadvantageous in that the number of parts and the amount of handling are increased, thereby increasing the manufacturing cost. Further, since the additional retaining members are provided on the tape side of the cushion sheet, the height of the member from the inner surface of the cushion sheet must be exactly controlled since, otherwise, the projecting end of the additional retaining member will come into contact with the magnetic tape. Thus the use of such additional retaining members introduces another difficulty in assembly.